Shut-down magneto check - advice

[FlyingGoat]

It seems fairly standard practice at the end of a flight to switch mags off one-at-a-time to check each ignition circuit (i.e. Lycoming).

I've also been advised by several instructors that switching off both together, and back on, checks whether either circuit is live with mags off. Sounds reasonable.

However, our Rotax 912 guru has made it clear that this is seriously dangerous practice on a Rotax, with the risk of shearing propeller bolts.

He also commented it was bad practice on a Lycoming (for example) as it would torque-shock both the crank and prop bolts.

I'd really appreciate hearing your opinions on this.

[Croqueteer]

:eek:Switching both off risks cracking the exhaust inside the heat exchangers resulting in fumes inthe carb or in the cabin.

[Shaggy Sheep Driver]

If you switch off the left mag and get a drop, ditto the right, neither mag can be permanently 'live' or you would get no drop when you switch it off. Ergo, no need to switch off both together then on again.

It's that last bit that can do harm. Some aeroplanes (such as the Chipmunk) don't have a lean cut off, so the engine has to be stopped by switching off both mags (and simultaneously going to full throttle). The latter obviates any tendency to 'run on', as incoming vapourised fuel is ignited by glowing carbon in the cylinder.

[worrab]

How many fractured prop bolts have you seen?

[FlyingGoat]

Thanks, guys.

Worrab - me none, our Guru experienced 2 on a 912 with the others loose (same engine)

[9 lives]

With a Lycoming or Continental engine at idle, briefly switching off both mags will do no harm, and is good practice in my experience. Any power while doing this may result in a damaging backfire in the exhaust, so idle only.

Your propeller bolts will be fine! Anything which "shock loads" your engine, you're going to feel as a shock in the fuselage, so you'll know it's happened. Careless pilots are doing more harm slamming in full power form idle, than could ever be caused by any power change in the idle power range....

I have too little experience with Rotax engines to offer a qualified comment for them. But, for any engine, a potentially damaging action/event will probably be mentioned in a flight manual limitation, or at least cautionary note. Are there any such for your aircraft?

[Shaggy Sheep Driver]

With a Lycoming or Continental engine at idle, briefly switching off both mags will do no harm, and is good practice in my experience.

Why is it good practice? It's potentially damaging and there's no reason to do it, so why would you?

[Heston]

The OP specifically referred to the Rotax 912. This engine is stopped by switching both ignition switches off. It does not have a mixture control or idle cut off. With this engine it is a nonsense to briefly switch both ignition circuits off and then back on again to "check that both circuits are off". Why? Because stopping the engine with the switches means that you have automatically checked that the ignition is off. If one circuit was still live, the engine wouldn't stop!!


Yes this does happen. To stop the engine if the switches don't kill it you have to switch off the fuel and wait til the carbs empty, or you can put on full choke.

[xrayalpha]

My experience is Rotax engines:

Why, on shut down, would one then put the mags back on?

We follow the procedures as set out by SSD above. One off/on, the other off/on, then both off. Listen for the mag drop.

Engine is now stopped, time for tea and biscuits.

Why would we flip them off and then hope there is enough enertia in the prop to give the required 300rpm so that the mags will allow the engine to fire up again if we flip them on? And then just switch it off?

Rotax's are like car engines, turn them on and turn them off - no running rich or lean etc.

To be frank, mags off engine stops. Quick as that! And the Rotax mags have a safety feature built in so that you need 300rpm on the prop to fire.

Ask anyone with a Rotax 912 - particularly the 912S - and the biggest problem for your engine mounts and sprag clutch is starting in winter and getting the engine to half fire, cough and splutter and not really get going. The kickback on the 912S is a real engine knackerer.

It also can eat engine mounts on C42s, Eurostars, Europas and weightshifts - from personal experience. With 4,000 hours on 912 powered C42s at Strathaven, we have some idea of what is good.

None of the above applies to legacy engines, no idea about 100ll guzzlers!

[boddamese]

I was always told never to switch off both mags when the engine is running.

My understanding is that if you switch off both mags the engine will continue turning on its momentum for several rotations, drawing in fuel and pumping it into the exhaust unburned. This risks a back-fire (i.e. fuel burns in the hot exhaust) with the risk of damage as mentioned above.

All that applies to Lycoming engine found in PA-28s etc. As for more modern fuel injected types I couldn't say if it's the same.

[Shaggy Sheep Driver]

It's not switching off the mags that's the problem, it's switching them off and then on again!

Apart from anything else, that's begging for a massive backfire (explosion in the exhaust) as the unburned fuel/air mixture is ignited by the next blast of hot exhaust gas as the engine re-lights. Try it in your car / on your motorbike some time. Switch off the ignition when driving / riding along, then on again. BANG! Damage to your exhaust baffles at best! (Probably won't work with modern electronic fuel injection as the injectors will shut off when the ignition is switched off. It's carburated and probably the simple non-electronic injection of aero engines where this will happen - Lycoming, Continental, Rotax, de Havilland etc).

And I ask again, WHY would you do it in any aeroplane anyway? What is the reasoning? Surely we don't have pilots doing daft things they haven't thought though?

[FullWings]

It's not switching off the mags that's the problem, it's switching them off and then on again!
Quite.

This is the story from the OP:
I've also been advised by several instructors that switching off both together, and back on, checks whether either circuit is live with mags off. Sounds reasonable.
I think I’d tell those instructors that they should consider what they’re advising from a technical standpoint.

If the “and back on” was left out it would sound better. As it is, no. If the engine stops when both mags are off, you’ve proved they’re working properly. If it carries on running, you have a problem.

Anyway, you should always treat an engine/propellor combination as liable to start at any time without warning. That way you won’t be caught out if by some miracle it happens...

And I ask again, WHY would you do it in any aeroplane anyway? What is the reasoning? Surely we don't have pilots doing daft things they haven't thought though?
Beats me. It’s not unique in the collection of odd behaviours with no rational explanation exhibited by pilots who should know better. Maybe it’s because there isn’t terribly much in the way of supervision, guidance and for want of a better word, oversight, once people are qualified and fly in GA. Plenty of space for funny little habits to form, especially if you’re an instructor somewhere out of the limelight.

[clunckdriver]

Some time back I was trying to check out an instructor on a Cessna 421, powered by "GITSO" engines, on the way to the run up pad I sugested he do a "dead mag" check, to my horror, and to the great distress of the gear box ,he shut of BOTH mags and then turned them back on, never did finish checking him out, and the gear box needed changing ten hours later, his career as a corporate pilot {not in my aircraft} lasted four trips before he bent a twin rather badly, so now he is back teaching students how to wreck engines, and all the other nonsense procedures which have crept into flight training on this side of the pond.{such as endless checklists in single fixed gear, fixed pitch trainers}

[9 lives]

And I ask again, WHY would you do it in any aeroplane anyway? What is the reasoning?

Sorry I could not reply to your first request for reasoning, I was outside clearing snow...

The mag switch closes a circuit to "turn a mag off" - it grounds the mag out. The fact that the "L" and "R" positions of the switch will turn off each mag in turn, is not a test that the switch "off" position is working to turn them both off. There are AD's on Mag switches for incorrect function.

I was trained to do live mag checks, at dead idle, as required, so I do them after some flights. This was vividly reinforced for me one day, while hand propping a friend's 150 (which I also flew regularly). I called "Mags off", he called back "mags off". I swung the prop to pull it through, and it started. Happy I always swing props like it's gonna start. I gave him a rather disgusted look through the prop arc. He held up the keys for me to see.

Twice, I have had to key "Off" an engine, as someone was approaching the prop, and I wanted it stopped fast. And, in a floatplane, sometimes you want the engine off at that moment, not idle cut off from now.

So, after careful reasoning, and some experience, I do live mag checks - at dead idle only, and for the briefest moment. Just enough to be sure it stopped. I've never had a problem doing that. Not every flight, if I know the plane, just time to time, or before water docking.

For aircraft types where the mags are switched by only two toggle switches, I would agree that two individual mag checks sum to the whole check, but for key type switches, I'm not convinced....

[Gertrude the Wombat]

there's no reason to do it
Depends how fast your plane is approaching the dock ... if you're on floats you don't have any brakes.

[gasax]

T directly answer the OP's question -you stop a Rotax to minimum revs and then switch off both mags. The engine will stop, if you have reduced the revs as far as possible with less violence than might occur otherwise. With my conventional mag type switch I can go to one mg and then off.

Switching them back on would cause senseless damage - as it would with a Lycon.

The 912S is a fierce little engine which normally stops as though it has seized, slowing it as much as possible reduces the strain on the mounts and prop.

Switching the mags back on - in any sort of engine is asking to shock load it, blow the exhaust to pieces or just plain stress it. Doing that on a Rotax is even worst, a high rpm, high compression engine should never be treated that way.

[Piper.Classique]

Step turn, the rotax typically has two separate switches, so turning them off one at a time does check that both mags are earthed.
Our usual procedure is to check individual mags at engine run up, then stop the engine by turning both mags off together.
Rotax engines do sound a bit solid when stopping....

[Shaggy Sheep Driver]

Step, if you do a mag check (left switch off, then on before doing same with right) and you get a drop in rpm when each switch is 'off' (grounding its mag) then you have not got a permanently live mag. If the mag was permanently live (un-grounded even with the switch in the 'off' position) then you'd get no mag drop when you selected that switch to 'off.

This is the same whether you have two toggle switches or a 'left, right, both' key switch.

[JAKL]

You'd have thought the manufacturer would have written some sort of manual that tells people how to start and stop the engines!

[smarthawke]

I'm with Step Turn on this one.

Firstly, different types of engine and engine control/operation here.

Rotax is simple - reduce rpm to idle, off with one ignition switch and rpm decays, off with the other and engine stops. Thus proving the switch is doing its thing.

Lycoming or other (non-Rotax) aero engines that have two independent ignition switches obviously behave like the Rotax.

Lycoming or other (non-Rotax) aero engines with a keyed ignition switch should be treated differently.

For sure, checking the 'left' and 'right' positions will tell one if in that position the switch is earthing out (switching off) one mag or the other.

The 'off' position may have an internal problem of its own therefore allowing one or both mags to be live. Hence, the 'dead cut' check is carried out - but only at idle where it won't cause a problem when the ignition is turned back on.

If someone goes to off accidentally when checking the mags at any rpm other than idle, then you're better off letting the engine stop completely and then restart it.

Personally, when checking mag timing on maintenance checks, I always try moving the key about in the ignition switch in all possible positions (including off) with the mag timing box 'on' to make sure the switch is behaving as it should. I've replaced a number of ignition switches over the years because of an intermittent live mag when the switch was in the 'off' position. I also check to make sure the key can't be removed in any position apart from when 'off' - again, I've found worn keys or switches that fail this check.

[Kinger]

A backfire is actually ignition in the induction side.

[Shaggy Sheep Driver]

A backfire is actually ignition in the induction side.

That sounds logical (the ignited gasses heading back down the intake), but I never heard of a 'front fire'.

'Backfire' has become the accepted term for fuel / air mixture exploding in the exhaust having passed unburned through the cylinder (because someone turned the ignition off then on, or on closing the throttle on a fast running engine when there's an exhaust air leak). The accepted term for it happening in the carb or intake (the induction side) is 'spitting back'.

Those of us who used to maintain our own (carburated) cars back in the day were very familiar with both as we struggled to get ignition timing and fuel mixture correct.

[Mach Jump]

Smarthawk has it absolutely right.


MJ:ok:

[A and C]

There is a Lycoming SB about shutting engines down, the main thrust of it is to prevent plug fowling, unfortunately no one above has even referred to this and the procedures it recommends.

Most of what I read above is just the rehashed flying club folk lore with little technical merit, Smarthawk being the one beacon of technical expertise in this very dismal thread.

[India Four Two]

Some aeroplanes (such as the Chipmunk) don't have a lean cut off

SSD,

I was surprised to read that. The T10s I flew in the 60s had a "slow-running cutout", consisting of a ring and a cable on the right side of the cockpit. I had to look up the Pilot's Notes to double-check my memory and I see that it was introduced as Mod H246. Originally T10s were shut down by turning off the ignition switches.

Further reading shows that the RCAF Chipmunks also had a slow-running cutout, but the Canadian civil ones did not.

Was the cut out removed when the T10s were placed on the civil register?

[glendalegoon]

wow, I guess I am dumb. granted I haven't flown a piston anything in over 30 years, but I never did a post flight mag check.

shut down with mixture, prop stops, remove key.

oh well.

lycoming was my main piston, continental too.

[Big Pistons Forever]

Smarthawk has it absolutely right.


MJ:ok:

I second what Smarthawk wrote :ok:

[Mach Jump]

None of the civvy chipmunks I've flown had the 'Ring pull' cut out, and some of the ex T10s had it removed. Most of them still had it though.


MJ:ok:

[xrayalpha]

A and C,

The OP was about ROTAX engines.

Perhaps being taught wrongly by those experienced on other types?

[mary meagher]

Inspired by Step Turn and Piper Classic's references to float planes... and to avoid thread creep, might be interesting to hear from you guys that have or would like to have experience on these aircraft. so I shall not entertain you here with my experience of using idle cutoff as an anchor when approaching the dock.....

Carry on with your mag checks....I've only set an engine on fire once, when overpriming a reluctant 152 when I was a learner....

[Shaggy Sheep Driver]

I can see Smarthawk's point about the 'off' position maybe having a fault, so by all means put mags to 'off' on shutdown. But as I keep saying the damage can be done when mags are switched off then on again while the engine is still turning.

So if you want to check both mags are 'off' in the 'off' position, turn the key to that. But why turn them on again having proved the engine stops firing?

Civvy Chippies I've flown were always switched off by switching off the mags and fully opening the throttle - there no other method (OK, you could turn the fuel off and wait a few minutes for the engine to stop!). In the engine compartment one could see where there used to be cable coming from the RH side of the panel, but I always understood that to have been to cycle the cartridge starter, which was removed when Chippys were civilianised.

[A and C]

I have no doubt whatsoever that the teaching is wrong, most of what I see taught at flying clubs is rehashed Gypsy procedures and limitations.

Lycoming do publish a shut down procedure I have never seen it carred out by a civil flying club.......... The RAF however do use the procedure writen in the Lycoming SB, I am guessing they are the only people who have bothered to read the technical data.

I have no doubt that there are still instructors reeling out the same rehashed Gypsy stuff for Rotax engines.

I doubt the prop bolts are the issue with the Rotax, I would hazard a guess any damage would result in the reduction gearbox or clutch.

[Mach Jump]

SSD:

On conventional Lycoming/Continental engines with rotary mag switches, you shut down the engine by moving the Mixture to ICO, then, when the engine has stopped, switch off the Mags. This not only prevents 'pre-ignition' ot 'running on' after switching off, but has the advantage that the engine is left in a doubly safe condition, as both the ignition is off, and the idle system is drained of fuel.

You carry out the 'Live Mag' check just before that, with the throttle closed, and the engine idling. The reason you put the mags back to 'on' is to enable the idle system to drain when you put the Mixture to ICO.


MJ:ok:

[9 lives]

You carry out the 'Live Mag' check just before that, with the throttle closed, and the engine idling. The reason you put the mags back to 'on' is to enable the idle system to drain when you put the Mixture to ICO.

That's always been my procedure (for Continental and Lycoming), never a problem.

The sense of abuse of aircraft piston engines seems entirely misplaced by some folk. An idling engine is pretty hard to abuse in the short term. What I would really like to see stopped is throttle jamming - in either direction. Pilots sitting on the runway, and jamming it open, or at altitude, jamming it shut. That's where expensive damage is being done! If you handled the control wheel or stick that way, you'd be damaging the airframe, how is the engine any different?

[Jim59]

It seems fairly standard practice at the end of a flight to switch mags off one-at-a-time to check each ignition circuit (i.e. Lycoming).

I always do it before shutting down (Lycoming) but only one at a time. One expects slight RPM drops to verify that the switch is grounding each mag. in turn. If the engine stops you have just detected a defective magneto.

I have had the engine stop when doing this at the end of the day after a flight. The magneto had failed and needed to be replaced. It meant that it was possible to get the aircraft fixed in a timely way and not find out about it only when starting the next time.

If it stops firing wnen one mag. is off then just let is stop.

[9 lives]

Jim59, will the post flight mag check as you have suggested, tell you if you could have a live mag after the engine has been stopped? The post flight check is often called a "Live Mag Check".

[ShyTorque]

I second what Smarthawk wrote

I "third" it.

The "dead cut" mag check technique was taught by the RAF on their Lycoming engined aircraft, which had a single rotary type magneto switch. This type of switch has three earthing contact positions in one switch, rather than two switches with an independent earthing contact in each. Two positions earth out one mag each, the "OFF" position earths them both.

Normal shutdown was from idle "Drop no stop, drop no stop, drop and stop, back to both" Then the fuel cutoff knob was operated to stop the engine from idle.

If a rotary mag switch has failed internally at the "OFF" position (i.e. the earth contact isn't earthing) and you stop the engine using the fuel cut off, you wouldn't know that one or both mags had been left in the ungrounded condition. So, the rotary switch points at "OFF" but both mags could be live.

At idle, the "shock" caused by switching the mags back on again is no worse than that caused by a partially fouled plug shorting out during taxying or during a power check, After all, only one cylinder fires at a time.

[Heston]

Makes perfect sense on an engine with a rotary "mag" switch and that is stopped by pulling the idle cut off. But no sense at all on a Rotax 912 or similar that is stopped by switching off the "mags" and that doesn't have an idle cut off.

[ShyTorque]

Which is why the manufacturer's advice should be sought out and followed, rather than hearsay from folks who have never read it.

[Mach Jump]

Yes. And this briings us nicely back to the original question.

Modern engines and systems have introduced new advantages but also new risks, and modes of failure.

Although a 'One Fits All' procedure may be ideal, and was quite common in the 'old days', different combinations of engines, installations and systems may require different methods of operation.

If you are unsure what you have, or how it should be operated, go back to the official sources of information, and only add to, or introduce variations to the official advice if you are absolutely sure that you are not introducing unknown risks by doing so.


MJ:ok:

Ps. Just to check that we're all using the same terms here: A 'Dead Cut' check is where you switch off the mags/ignitions one a a time to check primarilly for a faulty mag/ignition, when the engine will 'dead cut'
A 'live mag' check, is where both mags/ignitions are turned off to check that neither of them are still 'live' when they are both in the 'off' position.

[Whopity]

I find that many pilots don't know that the Mag Switch doresn't actually switch anything off. It is a shorting switch to earth the magnetos and prevent them from producing an ignition pulse that could start the engine if the propellor was turned.

The check simply identifies that the earth connection is in place, once the switch is opened, there is an assumption that the next time it is trurned OFF i.e. the switch is made (ON) it will perform the same function. As with anything mechanical it may not! In general, switches are quite reliable so the major function of the test is to ensure that the magnetos are both connected to the switch and that the switch is connected to earth; this can be achieved by checking L and R without the need to go to OFF which will allow unburnt fuel to be sent into a hot exhaust manifold where it may ignite.

[Shaggy Sheep Driver]

Whopity - all true, but all that's already been said more than once here, not least by me.

[Crash one]

Ps. Just to check that we're all using the same terms here: A 'Dead Cut' check is where you switch off the mags/ignitions one a a time to check primarilly for a faulty mag/ignition, when the engine will 'dead cut'
A 'live mag' check, is where both mags/ignitions are turned off to check that neither of them are still 'live' when they are both in the 'off' position.

I'm sorry but that seems to me to be exactly the same thing, unless in the case of the "live mag" check they are both switched off together, in which case, which one is keeping the engine running is unknown until a "dead cut" is done. Making the "live"check unnecessary.
Please forgive the pedantics.

[Shaggy Sheep Driver]

The confusion obvious on this thread is all to do with the peculiarities of using a rotary key switch to control the mags instead of a sensible toggle switch for each mag. All part of Cessna and Piper's attempts to make spam cans seem like motor cars rather than aeroplanes.

Aeroplanes which are proud to be such and don't feel the need to masquerade as road vehicles (Cubs, Chippys, Lancasters etc) use toggle switches. As all aeroplanes should.

[ShyTorque]

The confusion obvious on this thread is all to do with the peculiarities of using a rotary key switch to control the mags instead of a sensible toggle switch for each mag. All part of Cessna and Piper's attempts to make spam cans seem like motor cars rather than aeroplanes.

Aeroplanes which are proud to be such and don't feel the need to masquerade as road vehicles (Cubs, Chippys, Lancasters etc) use toggle switches. All aeroplanes should.

I know of a certain Tiger Moth where the passenger caught those "sensible" toggle switches with his sleeve so they got switched off, putting the aircraft down in a field.

BTW, there was no key on the piston engined RAF aircraft I flew. Just a rotary switch.

[Crash one]

So it seems one cannot switch off both, one at a time, with a key?
I'm happy with two toggle switches and no keys, far less confusing.

[Shaggy Sheep Driver]

If the pilot was in the back seat, why didn't he see the downward-pointing switches stick out of the side of the fuselage?

Where the switches are inside and one set is out of sight of the pilot (Chippy, for instance) they are guarded to prevent accidental switching off.

I knew a meat bomber pilot who had the last man out switch off the mags and take the key with him. Had they been toggles he could have just switched them on again instead of having to do a forced landing with no power!

Toggle switches rule! Only cars have key ignition! ;-)

[ShyTorque]

SSS, I've no idea why, but then I wasn't flying the aircraft. I think the pilot sensibly opted to concentrate on putting it down due to the low altitude at which it happened. It was flown out again once the issue was resolved.

I'm unsure why you seem so concerned why some aircraft were designed and built with a different system to the ones you have flown. It's simply a matter of learning a new technique and understanding why it's done the way it is on a new type. As I've said twice, there is no key on the type I flew for some years, just a rotary switch.

[Shaggy Sheep Driver]

Shy, I have extensive experience of both types of mag switch. I much prefer toggles for their unambiguous simplicity. The confusion shown on this thread is all to do with the key-operated type. The only reason spamcans have key ignition is because cars do. There is no other reason than 'style' to fit rotary key-operated mag switches.

In my book, practicality trumps style every time!

[ShyTorque]

Well, you asked this:


Quote:
With a Lycoming or Continental engine at idle, briefly switching off both mags will do no harm, and is good practice in my experience.

Why is it good practice? It's potentially damaging and there's no reason to do it, so why would you?

(Your question in bold) I wanted to point out why there is a reason to do it on some types.

It's misleading and potentially dangerous to put forward as "fact" something which is an opinion based on personal preferences. I've been caught out a couple of times in the past by pilot hearsay so now I always read up the manufacturer's requirements and advise others to do the same. ;)

I've looked up the Rotax 912, which was one of the engines mentioned by the OP in his initial question.

Does it actually have "traditional" self contained and self generating magnetos? Looking at the parts diagram, although there is a magneto excitation coil, there is an external electronic module and another coil shown, too. "Switching off the ignition" may not actually be earthing the system on this type as per a self contained mag, but rather disconnecting the live side. Which means we might be discussing completely separate issues as if they were one and the same.

[Shaggy Sheep Driver]

Shy, the horizontally opposed Lycoming / Continental is a crude old engine, just like all but the latest generation. Same technology as an old Brit motorbike!

There's nothing magic about them that requires different engine handling to those other types. Toggle mag switches would work perfectly well (and do in the Citabria and Cub, just two such horizontally-powered aeroplanes I have extensive experience of which use toggle switches). Why should a C150 or a PA28 be different?

[Jan Olieslagers]

Our usual procedure is to check individual mags at engine run up, then stop the engine by turning both mags off together.
Rotax engines do sound a bit solid when stopping.... Not having read all of the thread, I am probably repeating. But I do fly behind a 912UL - 80 hp, not an S.

I concur with the first part, I usually do it during taxi though some pilots religiously stop near the treshold to do it.

But I do not agree with the second part, exactly for the reason stated: cut one ignition, count three, cut the other. Engine stops much smoother.

@ShyTorque: the ignition on a Rotax does not use the traditional magneto's, but the dashboard switches still shortcircuit something or other to ground to disable it. If you want the full detail you'll have to find it, schematics are all over the www.

[ShyTorque]

Shy, the horizontally opposed Lycoming / Continental is a crude old engine, just like all but the latest generation. Same technology as an old Brit motorbike!

There's nothing magic about them that requires different engine handling to those other types. Toggle mag switches would work perfectly well (and do in the Citabria and Cub, just two such horizontally-powered aeroplanes I have extensive experience of which use toggle switches). Why should a C150 or a PA28 be different?

I'm quite well versed with the Lycoming. I'm an ex-RAF QFI and used to instruct on a UAS equipped with them and I was also the Chief Ground Instructor of same.

Why should they be different? Because the designer/manufacturer decided to make it so. If you don't like key equipped aircraft you don't have to fly them. I don't like them either, despite having learned to fly in them in my youth, but it's irrelevant.

My point is, if the aircraft you're sitting in isn't equipped with your preferred toggle switches but a rotary one instead, you really should follow the manufacturer's procedure, not your own based on experience from other types. The "dead cut" check is done for safety reasons. If you don't do it correctly, someone else could get injured.

JO,

Thanks, from what I've seen on forums, discussing problems with ignition on Rotax engines it appeared that these can fail due to power supply wiring external to the engine driven part. Unlike a traditional magneto, which has only external HT leads and a grounding lead to "switch it off".

[Jan Olieslagers]

power supply wiring external to the engine driven partIf that is your understanding you have either visited the wrong forum or read incorrectly.
On the "back" side of the 912/914 there is a flywheel carrying a magnet - or several, I'm not sure there. The magnet passes under a total of 11 pickup coils, producing a gust of power in each at every revolution.

4 coils drive the 4 spark plugs of the one ignition box, providing both timing information and power
4 more coils do the same for the second box
2 coils supply power to the charging circuit
the last coil gives tachometer information

At least this is my understanding, I'll be glad to learn better if I missed something. But there certainly is (or needs to be) no connection between the ignition system and the battery power circuit.

For as much as I heard, there are not often any issues with the wiring. The ignition boxes OTOH have a poor reputation, coming from motorbike maker Ducati. There must be alternative makes but I failed to find any information, up till now. Looking frantically though, as said the Ducati boxes have poor reputation and are quite expensive - for a microlighter's purse, at least.

[ShyTorque]

Jan, I think you misread my post. I never mentioned the battery circuit and there definitely wasn't a battery shown on the parts list and diagram I looked at.

What does the external "ignition box" from Ducati actually do? This was why I asked the question about the detail of this specific ignition system. Does the "ignition" switch turn off the LT side, rather than earthing it, as it does in a traditional magneto?

[Jan Olieslagers]

Well, that's a matter of wording - you did mention "power supply wiring", didn't you? As the wires from the flywheel coils to the ignition boxes provide both power and timing you may have meant those, but I understood you meant "wiring from the aircraft power circuit" and that's what there is not.

A pointer to the circuit you looked at would be helpful, though.

[ShyTorque]

A pointer to the circuit you looked at would be helpful, though

I haven't seen a "circuit" diagram and haven't mentioned that word until now. It was a parts diagram and list.

I've checked some more; it is a Ducati DCDI ignition (double capacitor discharge ignition), rather more complicated than the traditional self contained magneto type of the Lycoming. I understand there have been some issues with the Rotax's external connectors between the generator coils and the module and with the reliability of the modules themselves.

[Jan Olieslagers]

Sigh. You and I seem to have very different vocabularies. What's the difference between a schematic and a diagram?

If we really are going to squibble on words, there is in a 912/914 no "power supply wiring external to the engine driven part" and those ARE your words literally copied.

That said: yes, the Ducati electronics must be rather complicated, certainly more complicated than an electro-mechanical conception of a hundred years old, give or take. And as I already said, they have a poor reputation regarding reliability. But I heard nothing wrong about the connectors, they look like the watertight connector blocks one finds under every contemporary car's engine hood.

[Shaggy Sheep Driver]

My point is, if the aircraft you're sitting in isn't equipped with your preferred toggle switches but a rotary one instead, you really should follow the manufacturer's procedure, not your own based on experience from other types. The "dead cut" check is done for safety reasons. If you don't do it correctly, someone else could get injured.

I wouldn't refute that, it wasn't the point I was making. The point was that the rotary key-operated mag switch was introduced by Cessna and Piper in place of toggle switches for no good technical reason (Bellanca didn't do it with the Citabria nor Piper with the Cub, both using the same engine as a spam can). It simply complicates what should be a dead simple process, such as toggles give you.

And they did it purely for stylistic reasons (to ape the motor car). There is no technical advantage, indeed there is a disadvantage as it complicates the shut down process and introduces areas of uncertainty among neophyte pilots where none should exist, as this thread amply demonstrates. To say "just follow the manufacturer's instructions" is stating the bleedin' obvious, but it excuses the issue.

In short, it's a piss poor design; style at the expense of function, style at the cost of introducing unnecessary complication and potential for misunderstanding to trainee pilots who really don't need such distractions.

That is my point!

[Mach Jump]

I'm sorry but that seems to me to be exactly the same thing, unless in the case of the "live mag" check they are both switched off together, in which case, which one is keeping the engine running is unknown until a "dead cut" is done. Making the "live"check unnecessary.
Please forgive the pedantics.

Crash one:

Yes. Just to clarify: During a 'live mag' check you momentarily turn off both mags together and check that the engine cuts out.

This is only necessary where the 'both off' position of the switches is different from the 'left off/right off' positions, and the engine is stopped by a method other than switching the mags off; eg. leaning the mixture.

In short, it's a piss poor design; style at the expense of function, style at the cost of introducing unnecessary complication and potential for misunderstanding to trainee pilots who really don't need such distractions.

That is my point!

SSD:

I agree. But we have to operate the aircraft as they are, and not as we would like them to be.

Like it or not, rotary switches introduce added complication and extra modes of failure. We have to be aware of that and operate them accordingly.

By the way, rotary mag switches are not new, nor were they invented by the Americans.

MJ:ok:

[ShyTorque]

I agree. But we have to operate the aircraft as they are, and not as we would like them to be.

Yes, precisely, which is what the thread was actually about.

SSS, I posted a reply to your question, because you obviously didn't understand the need for the "Mags to off/dead cut" check on some aircraft. We may not like the answer, but it is the correct answer.

[Shaggy Sheep Driver]

Of course I understand it, Shy. Been flying the bleedin' things for decades, including a stint as a meat bomber pilot. My point is, it would not be necessary to introduce arcane operating practices if manufacturer's refrained from putting style before function!

[Crash one]

MJ. Thank you. And I would agree that switching both off momentarily will (provided both earths are good) pump un burnt fuel down the exhaust with whatever consequence depending on the duration of momentarily. I kill my Continental with two toggle switches, since it once had a Stromberg carb with no mixture control. Using mixture "idle cut" proves nothing and would allow me to shuffle off leaving the mags live if I forget! Perhaps the "stylists" would care to think of numpties like me.

[ShyTorque]

Jan, I'm not squabbling or squibbling but you seem to have taken rapid and undue offence because I asked a technical question! :)

You implied that I thought that the battery provides the power supply to the DCDI modules. It obviously doesn't because we both know full well that on aviation engines the requirement is for fully independent ignition systems.

On the Rotax system, it appears that induction coils and magnets on the engine (not the battery) supply the LT power for the ignition. This is supplied to electronic modules which presumably convert this to HT energy and from there it is fed to the spark plugs.

The reason I asked? Grounding a traditional magneto isn't the same as cutting off the LT power supply to the input side of an electronic module by switching/breaking the circuit with a key operated switch. If it is done via the latter method, there is no point doing a "dead cut" check. All you would have to do is to check for "mag drop" and switch off. This would fit in with the OP's engineer's advice.

BTW, The diagram I mentioned was a simplified picture showing numbered parts of the ignition components. Alongside it was a list of those numbered parts. If I had found a circuit diagram I could perhaps have worked out the answer and wouldn't have needed to ask here.

I've just tried to get an answer from my local aircraft engineer, who helps maintain a couple of Rotax engines. Unfortunately, he wasn't in the hangar.

[cockney steve]

Forgive me if i'm wrong, but AIUI, the Rotax employs electronic ignition modules. one assumes that these work by disconnecting the power-feed (switching off) Some transistorised (solid-state) stuff doesn't take kindly to shorting -out or open-circuiting..

When using ICO to stop, is the carburettor float-bowl still full of fuel?
If so,it's not much different, strangling the idle -fuel, to switching off the sparks.
Just as a mag-system will show a slight drop when each mag is grounded, both off will produce a sudden and distinctively quiet drop. A very brief transition through that switch-position is all that's required to confirm both mags are grounding-out correctly. under those circumstances,a backfire is unlikely..
Always treat a prop as potentially LIVE and you won't get a free lobotomy.:}

[Crash one]

The carb float bowl is still full, ICO just leans the mixture to far too lean to run ie: fresh air.

[dash6]

Nice to do whatever is recommended while you are letting the engine temps stabilise while just parked/running up to the dock or whatever.
Nothing will ensure the Mags won't be live next time you go near the prop.
Meat bombers always have a spare set of mag keys! SSD where have you been?

[stevef]

Rotary magneto switches -

https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcSOwIYxIS9HEKtu4iXzkVYnNK_eOPd_eGYlG7cxnnS 40QWZ3o26jQ

As found on DC3s for example. Admittedly not key-operated. Top centre switch kills both mags at the same time in an emergency.

[ShyTorque]

I've managed to get hold a copy of the Rotax 912 manual. Section 9.4 covers the electrics.

As I suspected, this type of engine doesn't actually have magnetos.

It's a CDI system powered by a generator on the crankshaft (the word magneto doesn't occur anywhere in the manual).

[Jan Olieslagers]

As you suspected, you have found out for yourself what I already told you in #52

the ignition on a Rotax does not use the traditional magneto'sCongratulations! There is no need to ask on a forum those questions you can answer for yourself.

And. if I may ask a technical question, what do you mean in #64 by LT power ?

[ShyTorque]

Jan, You seem to have some sort of personal issue anger here. You have received a lot of advice from quite a number of members over the years you have been a member of this forum. It would be nice if you could give something back and discuss genuine questions without sarcasm or anger showing through.

By the way, having read the Rotax manual, I noted that your description of the ignition system wasn't completely accurate and you admitted you weren't sure about it. You should already have the circuit diagram you asked me for. It's in the 912 manual, below the system description.

Regarding your question added in the edit. LT? As you told me to do, look it up for yourself and answer your own question.

[Jan Olieslagers]

In #52 and #54 I offered purely technical replies. Later reactions bewildered me and I answered up to that bewilderment. Everything else I leave up to you, and please spare me your (doubtlessly well meant) recommendations.

[9 lives]

In general, switches are quite reliable so the major function of the test is to ensure that the magnetos are both connected to the switch and that the switch is connected to earthI quite disagree. Some of these rotary key switches are notoriously unreliable, and subject to AD's (perhaps you read my earlier hand propping story?)

Toggle mag switches would work perfectly well (and do in the Citabria and Cub, just two such horizontally-powered aeroplanes I have extensive experience of which use toggle switches). Why should a C150 or a PA28 be different? There are lots of later model Cessnas and Pipers which use toggle or rocker switches for the mags, rather than a key switch - all of their twins. However, I expect that their singles were fitted with key switches just to add one layer of theft deterrent - they are easy to fly!

No one is saying that the key switch is a great design, or superior to the independent toggle switches, it's just the way about 100,000 very popular aircraft were built. With good maintenance, AND PROPER GROUND CHECKS, they work fine, so what's wrong with that?

Exhausts can be damaged by mags off and on at high power, so don't do that. But I have never heard of exhaust damage at idle, so what's the problem? A necessary check, with no downside, appropriate for 100,000 or so planes. 'Seems worth training and conducting to me.....

[Shaggy Sheep Driver]

I expect that their singles were fitted with key switches just to add one layer of theft deterrent

Since they are not very secure in that just about any key of approximately the right size will operate them, I'm sticking to my 'motor car' theory. A lot of 1950s spam can marketing was based on the concept of 'motor car of the skies'. ;)

[A and C]

In my role as an LAA inspector I have yet to encounter any aircraft constructed from spam cans ( or any other food storage device ).

Could you please illuminate me as to the type of aircraft you are referring to ?

[Shaggy Sheep Driver]

A and C. How did you spend long enough in GA to become such an inspector without coming across the expression 'spam can', which I have never found anyone but a not-aviation person not to understand. Or were you just posturing?

There is another type of 'spam can' that railway enthusiasts will know about, by the way.

[A and C]

Spam Can A derisive term used to discribe a metal stressed skin aircraft.

The term is one used in British aviation to deride those products who they don't consider " real aircraft". This backward facing attitude resulted in the demise of the British aviation ( and motorcycle ) industry's when they failed to make use of advancing technology to produce products that were relevant to a modernizing market.

[B]Example[B] last mass produced British designed light aircraft engine.... Gypsy Major ......... Can trace its roots back to about 1914.

Engine that most of this thread is about......Rotax, a modern and very efficient engine..... Built in Austria.

[Heston]

Hmmm, A and C, sort of... But "spam cans" don't use Rotaxes.


Its not a backwards facing term, its a term of derision aimed at aircraft that are flying cars (and probably have rotary mag switches ;) ). People who use the term don't think they are proper aircraft.

http://www.pilotfriend.com/training/flight_training/fxd_wing/eurostar.htm


Is this a spam can I wonder? Its metal, got a Rotax 912 and has separate toggle ignition switches...

[cockney steve]

Obviously, A&C, you are not a Monty Python fan.

Spam was, in the second world war, the only meat whichwas universally readily available......it was everywhere,incorporated into virtually any and every meat meal. It was the generic, go anywhere, use for everything,universal meat.........It's tin ,popular folklore adopted, as a synonym for a robust, one size fits all, substitutes for any other type
do anything, go anywhere aeroplane.

Perhaps it's the British sense of humour. As I see it, it's an affectionate term for an old faithful that's always there,readyand waiting.

OK, it's bland and mediocre, but consistent and reliable.

OK?

[9 lives]

Okay, so we've drifted to discussing spam cans again, because the reality of a live mag check having merit with a key type ignition switch has been established, so instead of accepting this, some would like to divert attention away from a rather narrow minded point of view....

I have visited the Spam Museum, and there is nothing to do with GA aircraft in there (they do have a Spam truck though, I got the toy).

Austin, Minnesota - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Austin,_Minnesota)

Spam Can is not a term used in North American aviation, other than to respond to UK posts. The can for spam is a very useful item, purposely designed to have usefulness beyond containing the meat. (flat sides). I have seen Japanese toys made from recycled spam cans from not long after WW2 (they put the printed side on the inside of the toy). Resourceful people. So I guess those who use the term, equate the can to the plane?

So the spam is the contents of the can [plane]?

I have flown many aircraft which were very certainly not spam cans. Their common traits were fun to fly, nostalgic, and requiring (thus developing) greater pilot skill. But they were all very much less utilitarian, quickly repairable and long life durable than the metal planes I have come to also like.

So for both the planes I own, I have chosen all metal, with key switches, and been very pleased with them both.

Since they are not very secure in that just about any key of approximately the right size will operate them

Very true, but parked beside another theft candidate with only two mag switches, the key plane will still be stolen last! :D That's all I care about!

Hmmm, A and C, sort of... But "spam cans" don't use Rotaxes

Cessna 162 Skycatcher - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Cessna_162_Skycatcher)

And then, I understand that the engine was changed to an O-200 because of market preference? (I don't know much about them, 'never flown one). I bet they had a key switch though! :E

One of things I really enjoy about GA flying is the opportunity to experience many types of planes, and design philosophies. Each have their own pluses and minuses, because every plane is a compromise. We learn to operate them as they were designed and understood, so even the operations can be different, and yes, something which is right for one plane, might be less than good for another - this is why we take familiarization training!

Having flown about 80 types of GA aircraft, I'm getting there. I am learning the nuances. I listen to others who know more than I about a type or system, and try to glean the best from it. So, when I fly the Tiger Moth, I'll check the petrol, fill the oil, and I won't return two mag switches to "on" with the prop turning, and the fuel on. But the key switch planes... I'll be "live mag" checking.....

[A and C]

If you are to follow SSD's Logic the Sport Cruiser is a Spam Can and it is powered by a Rotax.

The only diference is that the Rotax engine is likely to outlast the airframe, unlike most American airframes of similar constructuon that will outlast six or more engines.

[Shaggy Sheep Driver]

Spam Can is not a term used in North American aviation, other than to respond to UK posts. The can for spam is a very useful item, purposely designed to have usefulness beyond containing the meat. (flat sides).

Not a term used in NA? Maybe not for car-like aeroplanes with appallingly poor handling (that, for the elimination of any doubt, is my definition of Spam Can where aeroplanes are concerned. A and C was very wide of the mark in his assumption of my definition).

But was it not the Great Chuck Yeager who opined of the first generation US space capsules "in one of those you are not a pilot. You are just Spam in a can"?

So maybe there's another allusion to a certain type of disappointing aeroplane. ;)

Here's another spam can. Many of these were re-built and thus became much better machines:

http://locoyard.files.wordpress.com/2013/06/004-2013-mainline-bath-and-bristol-eastleigh-unrebuiltbattle-of-britain-class-34067-tangmere1.jpg

[9 lives]

Indeed it was Chuck Yeager who referred to an astronaut in a Mercury spacecraft as "spam in a can", though Chuck was perhaps ill informed, as it was Gordon Cooper who demonstrated the remarkable precision of maneuverability of the Mercury spacecraft by hand "flying" it through an excellent re-entry. Yes, I accept that the Mercury spacecraft looks a bit like a can. I think that Chuck would have been one of the very few people on earth who dare consider pilot astronauts as "spam". But, I will always defer to Chuck, as I admire him.

car-like aeroplanes with appallingly poor handling

Define "car". Are we talking Porsche 928? or a Lada?

I have flown some aircraft with appallingly poor handling compared to others: A DC-3 is terrible to fly compared to an RV-4. But the RV-4 can't carry your overnight bag. The DC-3 can carry the RV-4 and the overnight bag. The Beaver has pretty poor handling compared to the Chipmunk, but it can take a half ton of your stuff into a little lake 500 miles away, and return. By the way, how isn't a Chipmunk a North American "spam can" - the engine? We can fix that, they're STC'd with Lycomings! It's a matter of what you want the plane to do. Personally, I would rather carry someone, and something somewhere, and home again. But, that's just me, to each their own.

I could find something appalling about any aircraft I've ever had the pleasure to fly, but I choose not to look for that aspect. I'd rather think about how lucky I am to have flown all the different planes I have, and to own two, which suit my needs well, are completely within my budget, and live a one minute walk from my home. If I were to go around describing people's chosen aircraft as appalling, they would not invite me to fly - my loss! Instead, I fly all kinds, and I like that! Would I come back from a flight test and tell the owner that his plane is appalling? I'd never be hired again!

So new pilots out there, check the mags the way you were trained AND understand what you are checking for, and the implications of incomplete checks. If you're flying a Cessna floatplane, please do live mag checks for the safety of your docking. And.. don't go around calling other people's planes "spam cans" or "appalling", it's just rude for no good reason...

[Shaggy Sheep Driver]

By the way, how isn't a Chipmunk a North American "spam can" - the engine? We can fix that, they're STC'd with Lycomings!

What! A Chippy with a Lycoming is NOT a Chippy! The look, sound, and character of the aeroplane are completely ruined by such a carbuncle! Would you fit a vintage Bugatti with a modern VW diesel engine just because it would be more oil-tight? And of course the DHC 1 is Canadian!

I have hundreds of hours in C172s, a 205 and 180 (the latter two meat bombing - the 180 was almost OK), several tens in the C150 and PA38 and a handful (I'd have died of boredom were it more) in the PA28, including the Arrow. And many, many more in the Chippy, Cub, Yak52, Citabria and others, even the Tiger Moth with its awful ailerons and poor control harmony but bags of character that more than make up for that!

Brian Lecomber in one of his wonderful books described these spammy sort of aeroplanes as 'having the airman's art designed out of them'.

If you don't know what that means, or think 'so what?', I can never explain it to you.

[9 lives]

Sure, there are "art" aircraft, and yes, I've flown a couple. I like the RV-4 and Bellanca Viking. But who says that the only reason for a plane to exist with pride is so it can be art? Maybe "useful" in opposition to art has merit too! The Porsche is "art", the pickup truck is not. But sometimes only the pickup truck will get the job done, so why should that be criticized? None of the "art" planes I have flown will get my job done at all - not even poorly. They would be wrecked trying, or cost a fortune. But my two modest American non art airplanes get my job done between them very nicely, so why would anyone want to knock that?

One of my favourite "jobs" is to land and camp on this lake - 150 miles from the nearest settlement, and 270 miles from the nearest fuel. I can't think of any "art" plane which could do that, and get me home safely.



http://i1294.photobucket.com/albums/b617/jim246/IMG_2771_zps860fd446.jpg

Why would anyone want to disillusion a new pilot by allowing them to think we older pilots (or maybe you older "art" pilots) aren't completely happy to have them join our ranks as proud pilots, even if they did turn up to the fly in in a 150? Sure, they might like to fly the "art" plane, but they will be much less inclined to want to be an "art" pilot, if they don't like the self declared art pilots they meet along the way. I never made a friend in aviation by knocking their plane. I sure learned a lot about the fun stuff you could do in a plane by trying different ones!

So, having drifted this thread so far from magneto talk that no one would even recognize it. I shall stand proudly on the case I have made. If someone wants to start a thread on knocking other people's choice of planes, perhaps I'll respond there.....

[Shaggy Sheep Driver]

What the fcuk's an 'Art Pilot'? Someone who draws pretty pictures in the sky with smoke trails?

Step, this is the Private Flying forum. Most private pilots in UK fly for fun. If you want to shift freight or pax, try a 747 or A380.

There is no reason I can see that a weekend fun flyer's fun in their few expensive trips into the third dimension should be compromised by an aeroplane that handles as if the flight controls include a few yards of soggy sponge. Richard Bach expressed similar views in 'A Gift of Wings'. I didn't know how true his words were until shortly after (having been inspired by that book) I did a PPL on C150s.

In the Chippy or Yak, the stick is held finger-thumb, with the pressures so light it's almost done by thought rather than stick movement, with instant response from the aeroplane. It makes the aeroplane part of the pilot - an extension of the body.

In a spammy one rolls on some aileron. And nothing happens. So roll on some more.And it sluggishly deigns to follow your input, provided there isn't a gust the opposite way that it'd rather follow. These aeroplanes are driven, a bit like a big bus, rather than flown, like a bird.

And there is absolutely no reason why the 'airman's art' has been designed out of them that I can see.

Maybe it's like American cars which are great in a straight line but don't do corners, designed for 500 miles of dead straight Interstate. A Mustang will blow your socks off in a straight line, but an MX5 with a fraction the power is a far more rewarding drive in the UK Peak District and will leave the Mustang in the dust on the first corner.

Spammys - US horses on a UK course?

[Big Pistons Forever]

Step

We live in a country where GA still thrives and where you can actually just jump in your airplane and go somewhere. Those Brits are just jealous......

What! A Chippy with a Lycoming is NOT a Chippy!

.

You are right it is a Better Chippy. Having flown a Chippy with the piece of Shyte, boat anchor Dripsy Major, and one with a properly done 180 hp Lycoming conversion, I can say the Lycoming engined one was a far superior airplane.

Both the Dripsy and the Lycoming/Continental flat four designs originated in the 1930's. Which one is still in production and widely used ? I rest my case.

[A and C]

While SSD and his mates are sitting in the bar of the flying club drinking second rate lager and eating pork scratchings taking about intracasys of the Tiger moths slow roll rate the PA28R pilot is south of France with wife sipping a sharp white wine and eating lobster.

Aircraft are for going places and seeing the world, the stable predictable nature of the PA28 so derided by SSD is a real asset when you have done four hours IMC flying to get to the sun of the south of France.

The post war British aircraft industry built aircraft for the likes of SSD and failed to survive, the American industry built aircraft for people who wanted safe transport and is survived dispite the best efforts of the blood sucking lawyers.

If you build for the mass market you can also enable your industry to build specialist aircraft due to the volume of parts production and the availability at the entry level to aviation, build aircraft that have "sole" as SSD says and your market is a few old farts in the flying club bar........and half of them can't afford to fly the thing you have built !

[Shaggy Sheep Driver]

A and C - you just don't get it, do you? Someone with taste and sensitivity to fly a real aeroplane like a Chippy as opposed to an aerial motor car like a PA28 wouldn't go within a mile of a pint of lager!

Step - enjoy your Bugatti with its drip-free modern diesel engine. I'll enjoy the character of an original and use an oil tray. We have Lycoming Chippys over here for glider tugging, and they look and sound awful. A great flat conk instead of that slender dH nose, and no more lovely Gipsy blatter either. And the prop goes round the wrong way!

I suppose you'd put one in a Spitfire as well!

[A and C]

It's you that is missing the point, the aircraft you talk of are from an age when labour was cheap, parts expensive and air travel was only for the very ritch

The DHC-1 is a typical example, it costs lots to run, costs lots to maintain and flys very slowly. The only thing it is good for is as a military trainer ( and at that it is superb) and yet the very moment someone who has another role for the aircraft (in this case as a glider tug) and optimizes the aircraft for this role by putting a lower cost power unit in the front you witter on about the aircraft loosing its sole.

What the aircraft is doing now is economically pulling gliders into the sky at a cost that the less wealthy club members can afford...........you are thinking about the aircraft loosing its sole...........I am thinking about the glider pilots who are flying because they can now afford the aero tow and those who are NOT stuck on the ground because the Gypsy has quit for the umpteenth time.

Old aircraft do have there place but they need viewing as part of history NOT the only pure way to fly.

[Shaggy Sheep Driver]

A and C you continue to miss my point. And it's 'rich', and 'soul', by the way. ;)

Oh, and 'Gipsy'. And if they are handled and maintained correctly they are no less reliable (probably more reliable) than a Lycoming.

[A and C]

I agree that the Gipsy is as reliable as the Lycoming when properly maintained ........ The problem is that it takes twice as much labour to do so add to this the lack of new parts and you have a mix that is ........ Expensive !

To compare the O-360 and Gipsy major, a Quality overhaul by the likes of Nicolson McClarren of the O-360 will cost IRO £15 K, Vintech are the quality option for the Gipsy Major and you are unlikely to get charged any less than £30K.

The O-360 is likely to go to about 1000 hours untill a cylinder change is required ( thanks to some excellent work by the BGA on engine management ) and then go to the 2000 hour TBO may be further on extension.

Do you honestly think you a Gipsy to 1000 hours with no cylinder work ? And then go on to to 2000 hours without further work ?

I would guess that using a gipsy rather than a Lycoming to tow gliders would add a minimum of £3-4 to each aero tow and that is before we get into the extra down time for maintenance of the Gipsy.
Ask your average glider pilot to pay extra to be dragged into the air by an aircraft with sole ( sorry soul) and all you will get is a big line of gliders behind the aircraft with the Lycoming engine.

[Silvaire1]

I almost bought a Portuguese Chipmunk once on the basis of it being a fun plane and my affinity for 'antiquey' stuff. What turned me off was the engine, and the fact that on this example the owner literally had to mop pools of oil oil out the cowling with rags after every flight. I'd expected something more like a US or Russian radial but the Gipsy design isn't that advanced - its more like a 1920s engine.

Its a roughly similar situation with the local (US) Bücker Jungmanns - we have a great many locally, with the numbers having grown slowly but surely since the 60s. Over the years and with so many Tigre and (to a lesser extent) Walter Minor engine failures, the owners accepted reality. At least in compensation they climb at a tremendous rate now, don't leak and don't need to be treated like museum pieces. The Gipsys are more reliable than a Tigre but no less fiddly and leaky.

[Shaggy Sheep Driver]

Ask your average glider pilot to pay extra to be dragged into the air by an aircraft with sole ( sorry soul) and all you will get is a big line of gliders behind the aircraft with the Lycoming engine.

Quite possibly, but as I keep telling you, that is entirely beside my point, which you continue to miss with astonishing accuracy!

Mike - I'm not normally a spelling pedant, but in A and C's case I made an exception! ;)

[bcgallacher]

The Gypsy series of engines are derived from half a Renault V8 engine of WW1 - that is why the thread system on the nuts and bolts is metric. A Major Halford was the designer - later known for his involvement with early gas turbine engines.

[A and C]

So let my try one more time, you ridicule aircraft because they are NOT old unreliable, expensive, difficult to fly and lack mass market appeal.

It looks to me like the attitude that resulted in the end of both the British light aircraft and the Motorcyle industry's , Fortunatly the motorcycle industry has recovered with a range of modern motorcycles that meet the aspirations of the market.

The down side is that I see very little chance of the light aircraft industry recovering with the help of the backward looking attitude demonstrated by yourself.

May be I have missed your point, probably because I can't see it is worth making, this opinion has been formed over the last few years of dealing with one and a half Gipsy majors welded together to result in twice the problems, the result is a wonderful historic aircraft for flying on sunny days but I certainly don't see it as being superior to modern aircraft just because there is a section of aviation enthusiasts who think it is a classic British aircraft.

[Shaggy Sheep Driver]

A and C; miles out!

[A and C]

I don't think I will ever get close in your logic free zone........... thankfully !

[Shaggy Sheep Driver]

You said it, A and C. You appear to look at things 100% logically. That's daft where flying for fun is concerned; what's logical about spending lots of money going nowhere?

But it does explain your blindness to my viewpoint.

[Mach Jump]

I just can't believe that a thread about magneto checks is still running, six pages after the original question was answered. :eek:


MJ:ok:

[Pilot DAR]

still running, six pages after the original question was answered.

Indeed... Any more discussion about mags?

[FlyingGoat]

An experienced aero-engine engineer, who flies his own Rotax 912-powered aircraft, just made this comment to me:

In the "Shut down" checks, I personally would add throttle to idle immediately before the switching off......I find the engine shut off is much softer if the throttle is brought to absolute idle, then 1 mag switch turned off, followed 1 second later by the second switch. Note, I am not advocating letting the engine actually idle below 2200 for any real period of time.

I think that was mentioned previously on this thread.

Many thanks to all previous - much appreciated.

[Jan Olieslagers]

Cutting the ignition circuits separately, with a bit of time in between, was indeed already suggested in #52. I didn't think to mention reducing to idle, thinking that self-evident, but I now realise it isn't: from the few times I was a passenger behind a Lyco/Conti, I remember they are stopped by cutting the mixture, at fairly high rev (1200 rpm comes to mind?)
But yes, surely, slow the Rotax to idle before stopping it, that will bring less stress on the gearbox - even with a slipper clutch installed, as it should be.

Edit: idle on my 912UL is much lower than 2000, perhaps 1300 or 1400 rpm depending on temperature. The one thing I do take care about is to run it fast enough when very cold i.e. after the first start of the day. Sometimes as high as 3000 rpm, for the first few seconds, then gradually reducing.

[gasax]

to stop a Rotax reduce to minimum revs and then switch off both mags. The engine will stop, if you have reduced the revs as far as possible with less violence than might occur otherwise. With my conventional mag type switch I can go to one mg and then off.


which was post #13 with some typos.

But the critical point is to read the manual and do what your particular engine needs. Lycoming, deHavilland, Rotax are very different engines and should be treated that way - according to their manuals.

[Shaggy Sheep Driver]

Indeed. I know nothing of operating Rotax engines but having observed them in use I can see they might require very different handling to the old iron. The shutdown procedure for the Gipsy Major, for instance, calls for idle throttle, both mags 'off', then throttle fully opened.

The reason for the fully opened throttle is that if there are glowing carbon deposits in the cylinder to provide an ignition source, the engine might 'run on', albeit lumpily. Opening the throttle wide at such very low RPM (it's after the mags have been cut) reduces the vacuum in the throttle venturi to the extent that what is drawn into the engine is mostly if not entirely fresh air, so not combustible, and the engine stops with no tendency to run on.

[B19]

I would never turn both mags off and then back. Got over 18 years on my Lycoming 150hp and have never done it.:)